The technology of alkaline membrane fuel cells (AMFCs) has been developed to date with OH-ion conducting polymers (“ionomers”) with a poly{hydrocarbon} backbone. Such ionomers require significant water uptake to achieve sufficient ionic conductivity. The structure and specification of an AMFC is illustrated in, for example, US 2010/0021777, entitled “Alkaline Membrane Fuel Cells and Apparatus and methods for Supplying Water Thereto”, the entire contents of which are herein incorporated by reference
As the level of water uptake increases—likely over 50% by weight—the ionomer typically loses mechanical integrity, resulting in morphological changes and, in some cases, overall disintegration which causes strong loss of cell performance. The likelihood of such mode of failure is particularly high on the anode side of the AMFC, where water is generated during cell operation, according to:
Anode process: 2H2+40H—=4H2O+4e
whereas the AMFC cathode runs on a water consuming process:
Cathode process: O2+2H2O+4e=4OH—
and is therefore much less likely to face a structural challenge by buildup of excess liquid water.
To help stabilize the cell structure, cross-linking has been suggested by one of the present inventors in a prior application as means for chemical bonding across the electrode/membrane interface. That application is U.S. Pub. No. US 2011/0300466 entitled “Chemical Bonding for Catalyst/Membrane Surface Adherence in Membrane Electrolyte Fuel cells”, the entire contents of which are herein incorporated by reference.
The above application suggests that chemical bonding of a catalyst layer to a surface of an OH-ion conducting membrane or membranes is accomplished by cross-linking of polymer components across an interface between the catalyst layer and the membrane. According to the above application, both the anode side and the cathode sides of the catalyst layer-covered polymeric membrane (CM) are bonded by cross-linking with the polymeric components of the catalyst layer, either at the interface alone or with the cross-linking extending well into the catalyst layer. The methodology for cross-linking is disclosed in Paragraphs [0010] through [0016] of the above publication.